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Author  Topic: Missing Matter  
Syamsu Suspended Member (Idle past 3849 days) Posts: 1914 From: amsterdam Joined: 
 
cavediver Member (Idle past 1903 days) Posts: 4129 From: UK Joined: 
Yep :) We tend to discover new particles by their distinct decay processes  i.e. what we actually "see" are the decay products, and their characteristics are used to infer the characteristics of the parent particle. Stable particles don't decay much for obvious reasons :) But they can be revealed by the *missing* characteristics following a collision. Unfortunately, this is also how we can detect for extra dimensions, so it's not an easy task differentiating all of these possibilities. But with some good luck it can be done...
See SG's earlier post. Edited by cavediver, : No reason given.
 
Son Goku Member Posts: 1150 From: Ireland Joined: Member Rating: 7.2 
Whoops! I somehow forgot about one of the most important experimental results in quantum chromodynamics.
 
Fabric Member (Idle past 3931 days) Posts: 41 From: London, England Joined: 
Myspace!
 
cavediver Member (Idle past 1903 days) Posts: 4129 From: UK Joined: 
 
lyx2no Member (Idle past 2975 days) Posts: 1277 From: A vast, undifferentiated plane. Joined: 
Edited by lyx2no, : No reason given. Kindly âˆžâˆžâˆžâˆžâˆžâˆžâˆž When I was young I loved everything about cigarettes: the smell, the taste, the feel â€¦ everything. Now that Iâ€™m older Iâ€™ve had a change of heart. Want to see the scar?
 
cavediver Member (Idle past 1903 days) Posts: 4129 From: UK Joined: 
 
RAZD Member Posts: 20119 From: the other end of the sidewalk Joined: Member Rating: 3.8 
Virtual particles? So is the proton a particle or the intersection of these fields: wherever they intersect in the right pattern there be protons? I thought Feynman demonstrated that particles were the best explanation? And is this how we get to multidimensions with string theory? Thanks. by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
 
Son Goku Member Posts: 1150 From: Ireland Joined: Member Rating: 7.2 
It's both. A particle resulting from the interactions of fields.
Particles are basic excitations of the fields and provided that the fields are not too "active" they may be used to provide a description of the fields detailed enough to compare with experiment. Concentrating on the particles also makes calculations simpler and means terms in the calculation can be represented by diagrams. This was Feynman's method.
No, the extra dimensions of String theory arise from different considerations.
 
NosyNed Member Posts: 8860 From: Canada Joined: Member Rating: 4.8 
And? Don't stop there. What considerations?
 
Son Goku Member Posts: 1150 From: Ireland Joined: Member Rating: 7.2 
Hopefully I can outline things in decent way, although I've never actually been in String research. First of all you should know of a process called quantization. This is a standard mathematical procdeure where one turns a classical theory into a quantum theory. It twins a classical theory with a quantum theory, essentially giving a quantum version of that classical theory. Now when a physicist speaks of something like quantum field theory and String theory, we are not to be taken at our word. The objects these theories describe are not fields or strings. Rather those names refer to the kind of classical object described by the classical twin of these theories. For instance quantum field theory should be labelled the less catchy "Theory which is the quantum twin of a classical theory that describes feilds". Too cut a (very) long story short, several people for various reasons, came to the conclusion that a theory of Strings was the best way to incorporate gravity into a quantum mechanical framework. In order to find such a String Theory physicists used the technique of quantization to start with a classical theory describing strings and end up with its quantum twin which should describe gravity. However it was found that if one sticks to four spacetime dimensions this doesn't really work. The quantization process turns gives an inconsistent theory as the twin to the classical theory of strings. If one wants a mathematically healthy theory to be the result of the quantization process, you must crank up the number of dimensions.
 
cavediver Member (Idle past 1903 days) Posts: 4129 From: UK Joined: 
The simple answer is that when you formulate string theory in d spacetime dimensions, you obtain an anomaly which destroys the physical characteristics of the theory  however the anomaly contains a factor of (d10), so when d=10, the anomaly disappears. This is quite unusal  most physical theories work equally well in any number of dimensions  GR, electromagnetism, etc, and thus they give no clues as to what the dimension of spacetime should be. One exception is Supergravity, and interestingly string theory and Supergravity have now revealed themselves as simply different perspectives of the same (M) theory, despite very different origins, and they are the two trheories that actually give important clues to the dimension of spacetime. Edited by cavediver, : No reason given.
 
NosyNed Member Posts: 8860 From: Canada Joined: Member Rating: 4.8 
That's the first time I've had a tiny hint of what the math is like for M( etc) theory. I know that the whole thing would be incomprehensible to me but having just a hint is good. Can we take the next tiny step in adding a bit more detail? I know what some equations look like (Schroedinger's for example) and even understand a bit of what goes on there. What does the math we are talking about "look like"? Is it one equation? Lots? Does it have many variables, parameters? a few?
 
cavediver Member (Idle past 1903 days) Posts: 4129 From: UK Joined: 
We can start with a single Lagrangian and go on a long journey of discovery. It will involve many equations and expressions.
:eek: I'm trying to work out how and it comes back to me why nomatter how many Mickey Mouse undergrad string theory courses are introduced, it is most definitely an advanced postgraduate subject. To understand the fuss and get that 'wow' factor, you really need to be comfortable with Lagrangian formulations of General Relativity and Quantum Field Theory, and have some knowledge of the Renormalisation Group. And this is just the very beginning!! But it is a challenge, so I may well have a go. It may be good to start with an *easy* topic like Hilbert's Lagrangian formulation of General Relativity. How familiar are you with Lagrangian mechanics? Given the fundemental nature of this, it may even be good to start here. This could be a long journey...
 
RAZD Member Posts: 20119 From: the other end of the sidewalk Joined: Member Rating: 3.8 
I used to be very good at it ... 40 years ago. Not to brag, but I aced my math classes at Duke (could have majored), however, it has been ages since those gray cells were exercised. So be gentle ... (I do still have my math books though so that should help) Enjoy. by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •



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